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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

12283 results found.

  1. EP260618a: OHP/T193 optical observations
  2. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  3. EP260618a: EP-FXT follow-up observation
  4. EP260618a: LCO optical counterpart confirmation
  5. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  6. EP260618a: COLIBRÍ optical counterpart candidate
  7. GRB 260616A: NuSTAR detection of prompt emission
  8. GRB 260614B: NuSTAR detection of prompt emission
  9. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 260618B: Fermi-LAT detection
  11. IPN triangulation of GRB 260617A (short)
  12. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  13. GRB 260616A: Insight-HXMT detection
  14. GRB 260618B: Fermi GBM Final Real-time Localization
  15. EP260618a: EP-WXT detection of an X-ray transient
  16. GRB 260610B: AbAO optical observations
  17. GRB 260506B: cubesat Avion detection
  18. GRB 260618A: Fermi GBM Final Real-time Localization
  19. GRB 260617A: Fermi GBM Detection
  20. GRB 260616A: Fermi GBM Observation
  21. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  22. GRB 260617A: Fermi GBM Final Real-time Localization
  23. Konus-Wind detection of GRB 260616B/EP260616a
  24. Konus-Wind detection of GRB 260616A
  25. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  26. GRB 260616A: GECAM-B observation
  27. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  28. GRB 260429A: cubesat Avion detection
  29. GRB 260616A: Fermi-LAT detection
  30. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  31. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  32. GRB 260614A: AstroSat CZTI detection
  33. EP260616a: EP-WXT detection of a fast X-ray transient
  34. GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
  35. GRB 260616B: Fermi GBM Detection
  36. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  37. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  38. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  39. GRB 260616A: Fermi GBM Final Real-time Localization
  40. GRB 260614B: SVOM/ECLAIRs refined analysis
  41. GRB 260610B: Terskol optical observations
  42. GRB 260614B: GECAM-B observation
  43. GRB 260610B: SVOM/GRM observation
  44. GRB 260614B: SVOM/VT optical afterglow confirmation
  45. GRB 260614B: Fermi GBM Observation
  46. GRB 260610B: ALMA detection
  47. GRB 260614A: GECAM-B observation
  48. GRB 260614B: SVOM detection of a burst
  49. GRB 260614B: Fermi GBM Final Real-time Localization
  50. GRB 260611B: SVOM/GRM detection
  51. GRB 260614A: Fermi GBM Final Localization
  52. GRB 260610B: further Liverpool Telescope optical observations
  53. GRB 260610B: Fermi GBM Observation
  54. GRB 260610B / AT2026owq: GRANDMA optical observations
  55. GRB 260610B / AT2026owq: further SAO RAS optical observations
  56. IceCube-260610A: No candidates from the Zwicky Transient Facility
  57. IceCube-260610A: EP-FXT follow-up observation
  58. GRB 260611B: CALET Gamma-Ray Burst Monitor detection
  59. GRB 260610B / AT2026owq: SVOM/VT optical observations
  60. GRB 260610B / AT2026owq: OASDG optical observations
  61. GRB 260610B: IAC-80 Optical observations
  62. GRB 260610B / AT2026owq: SAO RAS optical observations
  63. GRB 260611B: Fermi GBM Final Real-time Localization
  64. GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
  65. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  66. GRB 260610B / AT2026owq: Early ATLAS observations
  67. GRB 260610B: TRT optical observation
  68. GRB 260611A: Fermi GBM Final Real-time Localization
  69. GRB 260610B: DDOTI optical observations
  70. GRB 260610B: GOTO optical counterpart candidate
  71. GRB 260610B: Fermi GBM Final Localization
  72. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  73. Konus-Wind detection of GRB 260601A
  74. IPN triangulation of GRB 260601A (short/hard)
  75. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  76. GRB 260610A: Fermi GBM Final Real-time Localization
  77. GRB 260609A: Fermi GBM Final Localization
  78. Konus-Wind detection of GRB 260604C
  79. GRB 260608A: Fermi GRB Observation
  80. GRB 260604C: AstroSat CZTI detection
  81. GRB 260604C: SVOM/ECLAIRs refined analysis
  82. GRB 260608A: SVOM/ECLAIRs refined analysis
  83. Konus-Wind detection of GRB 260607B
  84. GRB 260607B: GECAM-B observation
  85. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  86. GRB 260608C: Fermi GBM Final Real-time Localization
  87. GRB 260604C: further SAO RAS optical observations
  88. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  89. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  90. GRB 260608B: Fermi GBM Final Localization
  91. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  92. GRB 260607B: AstroSat CZTI detection
  93. GRB 260608A: SVOM detection of a burst
  94. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  95. GRB 260608A: Fermi GBM Final Real-time Localization
  96. GRB 260607A: TRT optical observations
  97. GRB 260604C: GRANDMA further observations
  98. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  99. GRB 260604A: SVOM/GRM detection
  100. GRB 260604C: Mondy optical observations: evidence of a possible brightening

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